Make an interaction between 2 shells in an axisymmetric model in ABAQUS.

[BUBAMARA]

Dear all,

I would like to make an interaction between 2 shells in an axisymmetric model in ABAQUS. I continue modelling an yeast cell wall and its cytoplasm. This is the first time I use interaction in ABAQUS. I selected the cytoplasm as a master surface and the cell wall as a slave surface. The interaction zone consists of a semicircular ones and the interaction property is hard contact as normal behavoiur in mechanical set up.

The problem is when I run the inp. file the error is in here, the master and slave share the same nodes. Well, I don t really know how to fix up this.

Thanks in advance for your help,
Regards,

Paula

 

[IceBreakerSours]

Could you please explain the problem that you are trying to model? I find it hard to believe that there is any contact at all! Even if there is some interaction at the wall, how will you ever get the parameters required? A link to a classic or new research paper would help too.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[BUBAMARA]

Dear IceBreakerSour,

Thank for your answer. I would like to understand how can I make a properly contact between 2 biologicals shells. As I wrote before, this is my first time doing interaction in Abaqus, so that I must say sorry. Second, I would like to explain that model represents yeast cell wall and its cytoplasm under High hydrostatic pressure, which is a new food emerging technology. In order to that, this yeast will be under 700 MPa but the real problem is there is no enough experimental data to use in my model, because all of this is really new.

Regards,

Buba

 

[IceBreakerSours]

I am still not sure if you've answered my question so let me rephrase it: Are there any two (or more) surfaces sliding past each other? Think of your knee joint, for example. The two condyles press against and slide past each other and this whole process varies with activity.

I understand that the cell wall is under pressure but what does that have anything to do with assigning interaction? All there is to it is that some surface (i.e., cell wall) is under pressure. Correct me if I am wrong.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[BUBAMARA]

Dear IceBreakSours,

Thanks again from your promt answer. The problem is that the cytoplasm ( high % is water) has an internal pressure. I would like to make the simulation with outside presure ( hydrostatic pressure) and I also would like to find which is the outside pressure to brake the cell wall and the cytoplasm gets free ( mechanical stress analysis in the wall) . I have to make an interaction so as the external pressure crosses the cell wall to the cytoplasm. I am including my .inp with more details
Thanks for your help and your patience too!

Buba

 

[IceBreakerSours]

Did someone else make this model? Have you ever ran this model? I see many oddities.

1. Mesh quality could be much better given the simplicity of the geometry.

2. The INP has no shell elements in it. [See the title of this thread]

3. The amplitude definition is unused. Likewise, a material named water tube is unused.

4. Surface definitions for contact are wrong. For example, the cytoplasm surface is the 'outer' surface of the entire half of the cytoplasm. However, the region along the mid-axis is never going to come in to contact with the cell wall, or will it?

5. To me, the cytoplasm is just a fluid in an enclosed fibrous chamber (i.e., cell wall). This is perhaps why the material property for the cytoplasm has a very high Poisson's ratio. Also, no tangential behavior (sliding) is defined in the interaction. I imagine it would be friction-less.

6. How will you assess "breakage" of the cell wall and let the cytoplasm go "free"?

7. The nodes are pinned down in all three degrees of freedom. What do you expect the nodes to do under pressure? Have you looked at the ODB? Why aren't there any stresses?

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[BUBAMARA]

Thanks again IceBreakerSours!

Actually I just concentrated my effort undestanding the interaction, so I restarted the model using only cell wall and the cytoplasm, not the water sourrindings. As I wrote before, I have never made an interaction .. this why I did not selected the properly surface and I decided to attach the file. As I concerned, this is the best way to learn!
The properties of cell and cytoplasm were taken from bibliography, and I have seen in some scanning electron micrography the pictures the cell wall will start breaking at 400 MPa.
I promise will correct the model.

Thanks for your help !

Buba

 

[IceBreakerSours]

Try to do this "thought experiment": Imagine bending your knee. If you looked at the anatomy, you will notice that the femoral condyles presses against and slides past the meniscus. Watch this video if you are not familiar with the human knee.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[IceBreakerSours]

Continued..

So, what you notice is one body pressing and sliding past another body.

Now, coming to your model, what makes you think the cytoplasm presses and slides past the cell-wall (or vice-versa)? I do not think there is any interaction at all! In fact, I think, you should be simulating a fluid-filled cavity inside a cell-wall.

Finally, there are *many* problems in the model that have nothing to do with interaction.

Good luck.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[IceBreakerSours]

I have attached an INP that runs successfully and does what you were trying to accomplish. However, note that most of the concerns I pointed out above still need to be addressed.

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[BUBAMARA]

Dear IcebreakerSours,

First of all, thanks a lot for your time and patience!. I trying to do my best step by step.. even I am microbiologist! I am would like to understand the influence of the stress on cell wall rupture, and hopefully, this model will help to deduce the cell wall stress ( microorganism disruption) for given values of external pressure.
I take into account what you suggest me about fluid-filled cavity inside a cell-wall.

thanks again!

Buba